Alan Kasindorf > MogileFS-Client > MogileFS::Client

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Module Version: 1.17   Source  

NAME ^

MogileFS::Client - Client library for the MogileFS distributed file system.

SYNOPSIS ^

 use MogileFS::Client;

 # create client object w/ server-configured namespace 
 # and IPs of trackers
 $mogc = MogileFS::Client->new(domain => "foo.com::my_namespace",
                               hosts  => ['10.0.0.2:7001', '10.0.0.3:7001']);

 # create a file
 # mogile is a flat namespace.  no paths.
 $key   = "image_of_userid:$userid";   
 # must be configured on server
 $class = "user_images";               
 $fh = $mogc->new_file($key, $class);

 print $fh $data;

 unless ($fh->close) {
    die "Error writing file: " . $mogc->errcode . ": " . $mogc->errstr;
 }

 # Find the URLs that the file was replicated to.
 # May change over time.
 @urls = $mogc->get_paths($key);

 # no longer want it?
 $mogc->delete($key);

DESCRIPTION ^

This module is a client library for the MogileFS distributed file system. The class method 'new' creates a client object against a particular mogilefs tracker and domain. This object may then be used to store and retrieve content easily from MogileFS.

METHODS ^

new

  $client = MogileFS::Client->new( %OPTIONS );

Creates a new MogileFS::Client object.

Returns MogileFS::Client object on success, or dies on failure.

OPTIONS:

hosts

Arrayref of 'host:port' strings to connect to as backend trackers in this client.

domain

String representing the mogile domain which this MogileFS client is associated with. (All create/delete/fetch operations will be performed against this mogile domain). See the mogadm shell command and its 'domain' category of operations for information on manipulating the list of possible domains on a MogileFS system.

reload

  $mogc->reload( %OPTIONS )

Re-init the object, like you'd just reconstructed it with 'new', but change it in-place instead. Useful if you have a system which reloads a config file, and you want to update a singleton $mogc handle's config value.

last_tracker

Returns a scalar of form "ip:port", representing the last mogilefsd 'tracker' server which was talked to.

errstr

Returns string representation of the last error that occurred. It includes the error code (same as method 'errcode') and a space before the optional English error message.

This isn't necessarily guaranteed to reset after a successful operation. Only call it after another operation returns an error.

errcode

Returns an error code. Not a number, but a string identifier (e.g. "no_domain") which is stable for use in error handling logic.

This isn't necessarily guaranteed to reset after a successful operation. Only call it after another operation returns an error.

force_disconnect

Forces the client to disconnect from the tracker, causing it to reconnect when the next request is made. It will reconnect to a different tracker if possible. A paranoid application may wish to do to this before retrying a failed command, on the off chance that another tracker may be working better.

readonly

  $is_readonly = $mogc->readonly
  $mogc->readonly(1)

Getter/setter to mark this client object as read-only. Purely a local operation/restriction, doesn't do a network operation to the mogilefsd server.

new_file

  $mogc->new_file($key)
  $mogc->new_file($key, $class)
  $mogc->new_file($key, $class, $content_length)
  $mogc->new_file($key, $class, $content_length , $opts_hashref)

Start creating a new filehandle with the given key, and option given class and options.

Returns a filehandle you should then print to, and later close to complete the operation. NOTE: check the return value from close! If your close didn't succeed, the file didn't get saved!

$opts_hashref can contain keys:

fid

Explicitly specify the fid number to use, rather than it being automatically allocated.

create_open_args

Hashref of extra key/value pairs to send to mogilefsd in create_open phase.

create_close_args

Hashref of extra key/value pairs to send to mogilefsd in create_close phase.

largefile

Use MogileFS::ClientHTTPFile which will not load the entire file into memory like the default MogileFS::NewHTTPFile but requires that the storage node HTTP servers support the Content-Range header in PUT requests and is a little slower.

edit_file

  $mogc->edit_file($key, $opts_hashref)

Edit the file with the the given key.

NOTE: edit_file is currently EXPERIMENTAL and not recommended for production use. MogileFS is primarily designed for storing files for later retrieval, rather than editing. Use of this function may lead to poor performance and, until it has been proven mature, should be considered to also potentially cause data loss.

NOTE: use of this function requires support for the DAV 'MOVE' verb and partial PUT (i.e. Content-Range in PUT) on the back-end storage servers (e.g. apache with mod_dav).

Returns a seekable filehandle you can read/write to. Calling this function may invalidate some or all URLs you currently have for this key, so you should call ->get_paths again afterwards if you need them.

On close of the filehandle, the new file contents will replace the previous contents (and again invalidate any existing URLs).

By default, the file contents are preserved on open, but you may specify the overwrite option to zero the file first. The seek position is at the beginning of the file, but you may seek to the end to append.

$opts_hashref can contain keys:

overwrite

The edit will overwrite the file, equivalent to opening with '>'. Default: false.

read_file

  $mogc->read_file($key)

Read the file with the the given key.

Returns a seekable filehandle you can read() from. Note that you cannot read line by line using <$fh> notation.

Takes the same options as get_paths (which is called internally to get the URIs to read from).

store_file

  $mogc->store_file($key, $class, $fh_or_filename[, $opts_hashref])

Wrapper around new_file, print, and close.

Given a key, class, and a filehandle or filename, stores the file contents in MogileFS. Returns the number of bytes stored on success, undef on failure.

$opts_hashref can contain keys for new_file, and also the following:

chunk_size

Number of bytes to read and write and write at once out of the larger file. Defaults to 8192 bytes. Increasing this can increase performance at the cost of more memory used while uploading the file. Note that this mostly helps when using largefile => 1

store_content

    $mogc->store_content($key, $class, $content[, $opts]);

Wrapper around new_file, print, and close. Given a key, class, and file contents (scalar or scalarref), stores the file contents in MogileFS. Returns the number of bytes stored on success, undef on failure.

get_paths

  @paths = $mogc->get_paths($key)
  @paths = $mogc->get_paths($key, $no_verify_bool); # old way
  @paths = $mogc->get_paths($key, { noverify => $bool }); # new way

Given a key, returns an array of all the locations (HTTP URLs) that the file has been replicated to.

noverify

If the "no verify" option is set, the mogilefsd tracker doesn't verify that the first item returned in the list is up/alive. Skipping that check is faster, so use "noverify" if your application can do it faster/smarter. For instance, when giving Perlbal a list of URLs to reproxy to, Perlbal can intelligently find one that's alive, so use noverify and get out of mod_perl or whatever as soon as possible.

zone

If the zone option is set to 'alt', the mogilefsd tracker will use the alternative IP for each host if available, while constructing the paths.

pathcount

If the pathcount option is set to a positive integer greater than 2, the mogilefsd tracker will attempt to return that many different paths (if available) to the same file. If not present or out of range, this value defaults to 2.

get_file_data

  $dataref = $mogc->get_file_data($key)

Wrapper around get_paths & LWP, which returns scalarref of file contents in a scalarref.

Don't use for large data, as it all comes back to you in one string.

delete

    $mogc->delete($key);

Delete a key from MogileFS.

rename

  $mogc->rename($oldkey, $newkey);

Rename file (key) in MogileFS from oldkey to newkey. Returns true on success, failure otherwise.

file_debug

    my $info_gob = $mogc->file_debug(fid => $fid);
    ... or ...
    my $info_gob = $mogc->file_debug(key => $key);

Thoroughly search for any database notes about a particular fid. Searchable by raw fidid, or by domain and key. Use sparingly. Command hits the master database numerous times, and if you're using it in production something is likely very wrong.

To be used with troubleshooting broken/odd files and errors from mogilefsd.

file_info

    my $fid = $mogc->file_info($key, { devices => 0 });

Used to return metadata about a file. Returns the domain, class, expected length, devcount, etc. Optionally device ids (not paths) can be returned as well.

Should be used for informational purposes, and not usually for dynamically serving files.

list_keys

    $keys = $mogc->list_keys($prefix, $after[, $limit]);
    ($after, $keys) = $mogc->list_keys($prefix, $after[, $limit]);

Used to get a list of keys matching a certain prefix.

$prefix specifies what you want to get a list of. $after is the item specified as a return value from this function last time you called it. $limit is optional and defaults to 1000 keys returned.

In list context, returns ($after, $keys). In scalar context, returns arrayref of keys. The value $after is to be used as $after when you call this function again.

When there are no more keys in the list, you will get back undef or an empty list.

foreach_key

  $mogc->foreach_key( %OPTIONS, sub { my $key = shift; ... } );
  $mogc->foreach_key( prefix => "foo:", sub { my $key = shift; ... } );

Functional interface/wrapper around list_keys.

Given some %OPTIONS (currently only one, "prefix"), calls your callback for each key matching the provided prefix.

update_class

    $mogc->update_class($key, $newclass);

Update the replication class of a pre-existing file, causing the file to become more or less replicated.

set_pref_ip

  $mogc->set_pref_ip({ "10.0.0.2" => "10.2.0.2" });

Weird option for old, weird network architecture. Sets a mapping table of preferred alternate IPs, if reachable. For instance, if trying to connect to 10.0.0.2 in the above example, the module would instead try to connect to 10.2.0.2 quickly first, then then fall back to 10.0.0.2 if 10.2.0.2 wasn't reachable.

PLUGIN METHODS ^

WRITEME

HOOKS ^

add_hook

WRITEME

add_backend_hook

WRITEME

SEE ALSO ^

http://www.danga.com/mogilefs/

COPYRIGHT ^

This module is Copyright 2003-2004 Brad Fitzpatrick, and copyright 2005-2007 Six Apart, Ltd.

All rights reserved.

You may distribute under the terms of either the GNU General Public License or the Artistic License, as specified in the Perl README file.

WARRANTY ^

This is free software. IT COMES WITHOUT WARRANTY OF ANY KIND.

AUTHORS ^

Brad Fitzpatrick <brad@danga.com>

Brad Whitaker <whitaker@danga.com>

Mark Smith <marksmith@danga.com>

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